Before you jump to any conclusions about your ear being wrong, I’d look a bit more closely at what exactly this decibel meter is measuring, and whether it is measuring it correctly. And I’d also look into whether what it is measuring is really want you want it to measure.
Loudness is a subjective issue, in that the human ear is not equally sensitive to all frequencies. This means that a sound with a lot of power at one frequency may be less loud than a sound with less power at a different frequency. If the latter sounds louder to your ear, it is because it is louder!
Or put another way, how you perceive the sound when listening through human ears is more relevant than the number a power measuring device puts on the sound. This is especially true in the case of musical instruments. So I would be much more inclined to say that the device isn’t measuring the right parameter, than to say that my ears are wrong.
It is possible to try to weight decibel measurements in such a way that they account for the relative loudness perceived by the human ear. You can read more about this is you look up A-weighting. So, one thing I’d be curious about is whether the decibel readings from your app are A-weighted or not.
Another big open question is whether the app is even working correctly. Why are you more inclined to believe the app than your own ears?
Just as an aside, I frequently run into this kind of issue with my cycling friends. We all go on a ride together, riding exactly the same route. At the end we compare the stats on our bike computers, and invariably different people’s computers have different distances for the ride, and different amounts of elevation gain. Differences are often different by several miles, and elevation differences differ by up to 1000 ft or so.
Having spent a career as a computer science professor, and having some pretty good insights into how these bike computers work, I am not really surprised by this, and just put it down to some obvious technological and algorithmic differences between the devices.
My cycling friends generally have a different reaction. Some react with genuine surprise, and comment how they could have sworn we all rode around the same route, together in a group. Almost all of them believe their own bike computer, unquestioningly, even when they disagree, while also holding onto the idea that we did all do the same route together.
When it comes to reporting the stats of the ride, the general consensus usually seems to be to take the longest distance, and the highest amount of elevation gain, even when these two numbers come from different bike computers, and where neither of them might be your own!
I see this as a fascinating human phenomenon. In many ways, it is quite similar to a life-long professional musician concluding that his ears are wrong about the sound of his own instrument, simply because an app on his phone said so.
I don’t mean this as a criticism Pancelticpiper, nor as an argument with Cybernight’s original comments regarding timbre. I’m just quite fascinated and baffled by the level of implicit trust people have with their electronic devices and apps.